This invention relates to a gas flow control device, and more particularly to an auxiliary air regulator suitable for use with an internal combustion engine and provided in a bypass passage detouring a throttle valve in an air intake passage in order to provide a suitable amount of air required for the startup of the engine when it is cold.
Generally, when an internal combustion engine is started under cold conditions, the combustion conditions are suboptimal, and friction losses increase, thereby increasing the load on the engine. Accordingly, it is necessary to increase the amount of air intake to the engine, as compared with the amount under normal, warm, running conditions.
Thus, in an engine with a fuel injection device, an auxiliary air regulator, which has a control valve that opens depending on temperature, has conventionally been provided in a bypass passage detouring a throttle valve in the intake air passage in order to increase the amount of air flow when the engine is cold and simultaneously to provide an auxiliary supply to the engine. In this way, starting of the engine from cold is improved.
The amount of auxiliary air required decreases as the warming-up of the engine proceeds, as shown in FIG. 1 of the accompany drawings, and therefore the auxiliary air regulator is designed to decrease the auxiliary amount of air supplied with time. First, two examples of prior art auxiliary-air regulators will be described in more detail with respect to the drawings. FIG. 2 of the drawings shows a cross-sectional view of a first prior art control device. A shutter means 1 has a shutter plate 1a provided in a bypass air passage 2 and pivotally supported by a pin 4 mounted in the wall of passage 2. The shutter plate 1a is engaged at one end with the end of a bimetallic strip 3 disposed within a bimetallic strip chamber 5 adjacent to the bypass air passage 2, whereby the shutter plate 1a rotates about pin 4 according to the displacement of bimetallic strip 3 to open and close the bypass passage. However, this device has necessarily a small clearance around the shutter plate in the vicinity of its pivoted point, which forms a communicating passage between the air flow passage 2 and bimetallic strip chamber 5. Thus, it is impossible to completely prevent leakage of air from the bimetallic strip chamber 5. The air pressure within air passage 2 is very low because of the effect of the engine intake on the downstream side of air passage 2 so that air leaks from the bimetallic strip chamber 5 to the air passage 2. Since this air leakage tends to cool bimetallic strip 3 and heat is radiated through the metallic wall of the bimetallic strip chamber 5, heating of bimetallic strip 3 by a heater 6 during warming-up of the engine is hindered. This deleterious effect is especially large when the ambient air temperature is low, which slows down the displacement of the bimetallic strip 3 thereby failing to displace the same to its correct predetermined position. This lowers the speed with which the shutter is closed and supplied the engine with more air than is required for the warming-up period. Further, the shutter is not completely closed by the time that the warming-up of the engine has been completed with the result that the engine continues to rotate at a speed higher than its correct predetermined value.
In order not to hinder the movement of the bimetallic strip 3, the heater 6 should be mounted only on a part of the bimetallic strip 3, which makes temperature control of the bimetallic strip difficult and induces errors in the displacement of the bimetallic strip, and therefore makes for unstable control of the engine.
A second prior art device, illustrated in FIG. 4, is disclosed in U.S. Pat. No. 3,618,890 to Hans-Dieter Bastam. This device has a cup-shaped member 10 of insulating material in a housing 11, a heater 12 on the bottom of the cup-shaped member, and a bimetallic coil 13 disposed above the heater. The bimetallic coil has at its center a vertically projecting stem 14 at the top of which is mounted a hollow cylindrical valve member 15. This valve member has an opening 15a in its side wall and a top opening 15b and is rotatably received in a valve seat 16 which has an outlet opening which registers with the top opening of the valve member, and an inlet opening which selectively registers with the opening in the side wall of the valve member, according to the rotational position of the valve member. Reference numeral 17 denotes an electric energy supply cable. This device tends to perform slow control of the amount of air supplied to the engine during the startup period because the stem of the valve member is mounted at the central, or inner, end of the bimetallic coil where the displacement is smaller than at the outer end of the bimetallic coil.
Both prior art devices are of the separate type. The first is adapted to be mounted as shown in FIG. 3 wherein reference numeral 20 denotes the auxiliary air regulator, reference numeral 21 a throttle chamber, reference numerals 23, 24 rubber hoses, reference numeral 25 an air cleaner, reference numeral 26 an air flow meter, reference numeral 27 a throttle valve, reference numeral 28 a cold start valve, reference numeral 29 a fuel injector, reference numeral 30 intake air valve, reference numeral 31 an ignition plug, and reference numeral 32 a piston.
The second prior art device is adapted to be mounted on a flange or chassis 18 of a motor vehicle, as shown in FIG. 4. These devices use rubber hoses and clamps or other connecting means to connect their inlets and outlets to points in the throttle chamber upstream and downstream respectively of the throttle. The use of such hoses and clamps increases manufacturing costs, is more inconvenient from the point of view of the arrangement of other components, and increases the number of joints thereby lowering the reliability of airtightness.